1,720,957 research outputs found
Traffic analysis at short time-scales: an empirical case study from a 3G cellular network
No full textThe availability of synchronized packet-level traces
captured at different links allows the extraction of one-way delays
for the network section in between. Delay statistics can be used
as quality indicators to validate the health of the network and to
detect global performance drifts and/or localized problems. Since
packet delays depend not only on the network status but also on
the arriving traffic rate, the delay analysis must be coupled with
the analysis of the traffic patterns at short time scales.
In this work we report on the traffic and delay patterns
observed at short timescales in a 3G cellular mobile network.
We show that the aggregate traffic rate exhibits large impulses
and investigate on their causes. Specifically, we find that highrate
sequential scanners represent a common source of traffic
impulses, and identify the potential consequences of such traffic
onto the underlying network.
This case-study demonstrates that the microscopic analysis of
delay and traffic patterns at short time-scales can contribute
effectively to the task of troubleshooting IP networks. This is
particularly important in the context of 3G cellular networks
given their complexity and relatively recent deployment
On Robust Estimation of Network-wide Packet Loss in 3G Cellular Networks
No full textIn this work we present a novel scheme for statistical-based anomaly detection in 3G cellular networks. The traffic data collected by a passive monitoring system are reduced to a set of per-mobile user counters, from which time-series of unidimensional feature distributions are derived. An example of feature is the number of TCP SYN packets seen in uplink for each mobile user in fixed-length time bins. We design a change-detection algorithm to identify deviations in each distribution time-series. Our algorithm is designed specifically to cope with the marked non-stationarities, daily/weekly seasonality and longterm trend that characterize the global traffic in a real network. The proposed scheme was applied to the analysis of a large dataset from an operational 3G network. Here we present the algorithm and report on our practical experience with the analysis of real data, highlighting the key lessons learned in the perspective of the possible adoption of our anomaly detection tool on a production basis
A Distribution-Based Approach to Anomaly Detection for 3G Mobile Networks
No full textIn this work we present a novel scheme for
statistical-based anomaly detection in 3G cellular networks. The
traffic data collected by a passive monitoring system are reduced
to a set of per-mobile user counters, from which time-series of
unidimensional feature distributions are derived. An example of
feature is the number of TCP SYN packets seen in uplink for
each mobile user in fixed-length time bins. We design a changedetection
algorithm to identify deviations in each distribution
time-series. Our algorithm is designed specifically to cope with
the marked non-stationarities, daily/weekly seasonality and longterm
trend that characterize the global traffic in a real network.
The proposed scheme was applied to the analysis of a large
dataset from an operational 3G network. Here we present the
algorithm and report on our practical experience with the
analysis of real data, highlighting the key lessons learned in the
perspective of the possible adoption of our anomaly detection
tool on a production basis
Traffic monitoring and analysis in 3G networks: lessons learned from the METAWIN project
No full textA 3G network is a magnificently complex object embedded in a highly heterogeneous and ever-changing usage environment. It combines
the functional complexity of the wireless cellular paradigm with the protocol dynamics of TCP=IP networks. Understanding such
an environment is more urgent and at the same time more difficult than for legacy 2G networks. Continuous traffic monitoring by means
of an advanced system, coupled with routine expert-driven traffic analysis, provides an in-depth understanding of the status and
performances of the network as well as of the statistical behaviour of the user population. Such knowledge allows for a better engineering
and operation practice of the whole network, and specifically the early detection of hidden risks and emerging troubles. Furthermore,
the exploitation of certain TCP=IP dynamic behaviour, particularly the TCP control-loop, coupled with information extracted from
the 3GPP layers, provides a cost-effective means to monitor the status of the whole network without requiring access to all network
elements. In this article the main lessons are summarized learned from a two-year research activity on traffic monitoring and analysis on
top of an operational 3G network
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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